Photographic element overcoated with alpha screening dye



Sept. 20, 1932. E MEES R 1,878,961

PHOTOGRAPHIC ELEMENT OVERCOATED WITH A SCREENING DYE Filed April 28, 1930 Fig.1.

Emulsion Layer 4.

Emulsion 7.

Film 1.

gwwmloz Charlesl'lICMee-s,

Light.

Patented Sept. f 20,. 1931 d UNITED STATES .cmms E. xnmmrn mans, ornocmis'rm, mm sonic,- assrenon 'ro menus xonax comm, or nocnns'rns, NEW YORK, a conrona'rron on NEW YORK PATENT OFFICE PHOTOGRAPHIG ELEMENT OVEBCOATED WITH A. SCREENING DYE- Application. filed a rn as, 1930. Serial No. 447,828.

This invention relates to a photographic element and particularly to one in which is used a screening or overcoating dye for color photographic purposes, and especiallyto the use of screening dyes for motion picture film employed in certain methods for taking color motion pictures.

Intakingstill or motion pictures in color with superimposed films or emulsionssensitized to different colors, it is desirable to interpose between certain of the light sensltive layers screening layers which prevent certaln rays from aiiecting the underlylng emulsion. For example, in a two colorprocess, a green sensitive film and a red sensitive film are used with their emulsion surfaces practically contact, the picture exposure being made through the support side of the green sens1- tive film. The green sensitive emulsion is given a thin top coat of a green absorbing substance which prevents the green rays from afl'ecting the red sensitive emulsion which has a certain sensitivity to green. This green absorbing substance must not difi'use into the green sensitive layer to any marked extent. There are a number of commercial color motion picture processes which employ such red and green sensitive films face to face.

. One object of the present invention is the preparation of such non-diffusing screening layers for coating upon sensitive emulsions.

Another object is to provide such a screening'layer which will not penetrate too far into the emulsion but will be confined to a thin surface layer. I

A further object is toprovide a colored overcoating which does not desensitize the emulsion over which it is coated.

A still further object is to provide a screening layer which will wash outor fade suitably in the processing baths. that is, the ordinary solutions used for developing and fixing the film, so that the film in question, which is a negative, may be-reiidily printed to produce the positive.

Other objects and advantages willbe apparent from the following specificatiom I 7 do not limit myself to two color processes nor to the particular colors or dyes mentionedas examples.

1 It is to be understood that I apply the dye to the photographic emulsion in the form of a very thin overcoating. By overcoating I mean applying a thin layer on top' of the sensitive emulsion, as distinguished from bathing or dyeing as commonly understood. By the latter methods it is diflicultto properly restrict the penetration of the dye. If the dye penetration could be restricted, bathing or dyeing would be satisfactory.

Reference will now be made to the accompanying drawing.

Fig. 1 is an enlarged section of a film embodying'my invention.

Fig. 2 shows in section two films face to face as employed in the method of color photo- 'graphywith which my invention may be rection of the light-is from the support side, as shown by the arrow. The dye layer may be considered as consisting of dyed particles a relatively short dlstance into the emulslon layer. The diof silver. halideand of gelatin, the number of these particles (concentration) in a given area, being very high on the top surface, but becoming less and less with increasing depth. At a relatively short distance (a practically microscopic thickness) there are no longer any of these dyed particles.

In considering the screening action of these minute color filters, it must be remembered .that they absorb light of the color to which the emulsion in whichthey lie issensitive. Therefore, any dye ;..rticles which mav be in the lower portion of the dye layer, and tof ward the light, will screen oil or absorbthe light to which the particles behind them (toward the surface of the dye layer) are sensi tive. It will, therefore, be seen that if'the dye layer penetrates to considerable depth,

a great many of the sensitive halide particles of the emulsion will be screened off from the light which canact upon them, as there will be more of such particles with dyed screen- 'ing particles between them and the light.

The result is that the dye layer reduces the efiectiveness of its own emulsion layer and in effect the emulsion and'dye layer screens itscreen every separate particle from the action 7 of light of certain wave-lengths, usually blue,

violet and ultra violet. Therefore it is desirable to have the dye penetrate as deeply as possible or to permeate the whole emulsion layer. For this reason the dye is usually added to the emulsion before coating.

The class of dyes which I have found particularly advantageous for use as screening dyes are those known in the photographic art as sensitizing dyes. They are ordinarily used to add to photographic emulsions to confer color sensitiveness on them. The dyes which I use are of two classes. known as the acid sensitizing. dyes and the basic sensitizing dyes. These dyes may be used either,

from alcoholic solutions or from water solu-- iions. Slightly different results are obtained y the use of the two solvents, and some of the dyes in particular work better one way than F another, that is, some of the dyes of these results in water solutions only, while a few classes, for example, do not give satisfactory give better results from water.

I use the term dye in the same sense in which it is customarily used in this art, name- 1y, to refer to the dye itself or to any of its salts having the same characteristic properties.

Examples of the acid sensitizing dyes are the following: mono-chlorfiuorescein, dichloriiuorescein, tetra-chlorfiuorescein,monobromfiuorescein, di-bromfiuorescein, tetra" pseudo-cyanines, carbocyanines, oxycarbocyanines, thiocarbocyanines, kryptocyanines,

styryl pyridines and styrylquinolines.

The acid sensitizing dyes are usually employed in the form of their ammonium salts, on account of their superior solubility in alcohol and in water, and because they dry to 3.

smooth adherent surface. As an'example of then use for dye overcoatings, a solution is -made of the following formula (Formula 1) and this is applied by means of the usual coating apparatus or machinery in the form of a thin coating on top of the previously coated and dried emulsions.

Formula I Tetra-iodofluorescein f0 grams Ammonia, ,4; strength 6. cc. Denatured alcohol 300 cc.

' B Fluorescein ,40- grams Ammonia, strength cc. Denatured alcohol 700 cc.

An example of a basic sensitizing dye used in alcoholic solution is the following:

Formula II Rhodamine 6-G 8 grams Pinaflavol p-toluene suiphonate 32 grams Denatured alcohol 1,000 .cc.

Although thealcohol used in'this formula contains a small amount of water, it is desir- (It is usually best to dilute the above total able to add a little more water to increase the ease of spreading of the solution. Formula II is one which washes out entirely after processing.

An example of a sensitizing dye applied froma water solutionis the' following:

Formula III 1':2 dieth 1 3:4 benzo thio 'isocyanine iod de L. 1 10, 000 in water Where it is permissible to use water solutions, it isgenerally found that the sensitizing effect is increased, that is, the dyes not aggregates, these dyes usually consisting of very large molecules (chemically speaking).

On the other hand, alcohol has other advantages in that it prevents'swelling of the gelatin during coating and permits rapid drying, both of which result in less penetration of the dye into the emulsion.

Fig. 2 shows two films face to face, one of them overcoated by my invention, as they would ordinarily be employed in multicolor motion picture processes of the t pe described in the United States patent-to ves 1,320,760, granted November 4, 191 0 and the British patents to Buchanan, 12,469 of 1914 and Batmost of the dyes which tend to form colloidal tistini, 873 of 1915. Film 1 is the green sensitive component already described and Film 2 comprises a support 6 with a veryfast red sensitive emulsion 7 which is in intimate contact with the emulsion of Film 1. Exposure is made through the support of Film. 1 as Color screen surface coatings made with the dyes-mentioned above, and 1n the manner indicated, have, in general, several advanta es overthose made with other dyes hereto ore used for the purpose. (1) They penetrate the emulsion'to a minimum extent, providing a thin surface dyed layer; (2)' They do not fog or desensitize. In some cases, particularly where the dyes are used in water solutions, the sensitiveness is actually enhanced by the dye due to its sensitizing action. (3) They are easily removed or. changed to such tints as are not objectionable. 'I consider asincluded in my invention all modifications and equivalents coming within the sec e of the appended claims.

What claim is: 1. A photographic element conriprisingv a support, a sensitized layer thereon, and a go very thin layer of light restraining dye of a sensitizing type applied directly to the outer surface of the emulsion layer but not penetrating substantially into said layer, said dye being selectedfrom the cup consisting of the iso-cyanines, pseu o-cyanines, carbocyanines, oxycarbo-cyanines', thio-carbo cyanines, krypto-cyanines, styryl-pyridines, styryl-quinolines and the aciddyes of the fiuorescein series. so 2. A phonographic element comprisin a support, a sensitized layer thereon, an -a very thin layer-of light restraining dye of a sensitizin type applied directly to the outer surface 0 the emulsion layer but not penetrating substantially into said layer, said dye being an ammonium salt of a .dye selected from the group consisting of the iso-cyanines,

' pseudo-cyanines, carbo-cyanines, oxycarbo- Fcyanines, thiocarbo-cyanines, krypto-cya- 40 nines, styryl-pyridines, styryl-quinolines and the acid dyes of the fiuorescein series.

3. The method of overcoating a photo- 4 graphic emulsion with a dye which comprises applying. to the surface a very thin coat of f '45 a solution containing alcohol and a sensitizing dye selected from the group consisting of .the lso-cyanines, pseudo-cyanines, carboc'yanines, oxycarbo-cyanines, thio-carbo-cyanines, krypto-cyanines, styryl-pyridines, the a styryl-quinolines, and the acid dyes of the fiuorescein series.

Signed at Rochester, New York this 22nd day of April, 1930. p

CHARLES E. KENNETH ll/HEES. 

